Jiyun Park

Contact Transfer Printing of Side Edge Prefunctionalized Nanoplasmonic Arrays for Flexible microRNA Biosensor

For a nanoplasmonic approach of wearable biochip platform, understanding correlation between near‐field enhancement on nanostructures and sensing capability is a crucial step to improve the sensitivity in biosensing. A novel and effective method is demonstrated to increase sensitivity with the enhanced electric fields and to reduce noise with targeted functionalization enabled by transferring side edge prefunctionalized (SEPF) nanostructure arrays onto flexible substrates. Nanostructure sidewalls have selective biochemically functional terminals for the hybridization of microRNAs (miRNAs) and the immobilization of resonant nanoparticles, thus forming hetero assemblies of the nanostructure and the nanoparticles. The unique configuration has shown ultrasensitive biosensing of miRNA‐21 in a 10 × 10−15 m level by a red‐shift in scattering spectra induced by a plasmon coupling. This ultrasensitive SEPF nanostructure arrays are fabricated on a flexible substrate using a contact transfer printing with a release layer of trichloro(1H, 1H, 2H, 2H‐perfluorooctyl)silane. The introduction of the release layer at a prefunctionalizing step has proven to provide selective functionalization only on the sidewalls of the nanostructures. This reduces a background noise caused by the scattering from nonspecifically bound nanoparticles on the substrate, thus enabling reliable and precise detection.

One-step electrochemical fabrication of vertically self-organized silver nanograss

Fabrication of one dimensional metal nanomaterials offers many beneficial aspects due to their unique size- and shape-dependent characteristics. However, facile fabrication of a robust one dimensional nanostructure has still remained a great challenge. Here, we developed a new synthetic route of one-step electrochemical deposition of silver nanograss without the assistance of a template. By applying an overpotential of −2.0 V (vs. Ag/AgCl) under aqueous alkaline conditions, silver nanograss with a slight tilt in a randomly oriented direction was spontaneously formed on the working electrode surface. Two applications that utilize advantageous features of this silver nanograss were demonstrated: (i) an efficient surface-enhanced Raman scattering substrate for a chemical sensor and (ii) an enzyme-less hydrogen peroxide sensor. Compared to silver nanowire arrays fabricated using anodized aluminum oxide (AAO) templates, the silver nanograss exhibited comparable hydrogen sensing due to its catalytic hydrogen peroxide reduction activity and produced a much stronger surface-enhanced Raman spectroscopy (SERS) signal due to its innate structure.

Fabrication and Simulation of Fluid Wing Structure for Microfluidic Blood Plasma Separation

Human blood consists of 55% of plasma and 45% of blood cells such as white blood cell (WBC) and red blood cell (RBC). In plasma, there are many kinds of promising biomarkers, which can be used for the diagnosis of various diseases and biological analysis. For diagnostic tools such as a lab-on-a-chip (LOC), blood plasma separation is a fundamental step for accomplishing a high performance in the detection of a disease. Highly efficient separators can increase the sensitivity and selectivity of biosensors and reduce diagnostic time. In order to achieve a higher yield in blood plasma separation, we propose a novel fluid wing structure that is optimized by COMSOL simulations by varying the fluidic channel width and the angle of the bifurcation. The fluid wing structure is inspired by the inertial particle separator system in helicopters where sand particles are prevented from following the air flow to an engine. The structure is ameliorated in order to satisfy biological and fluidic requirements at the micro scale to achieve high plasma yield and separation efficiency. In this study, we fabricated the fluid wing structure for the efficient microfluidic blood plasma separation. The high plasma yield of 67% is achieved with a channel width of 20 μm in the fabricated fluidic chip and the result was not affected by the angle of the bifurcation.